Ceramic bead catalysts in a packed bed have been used for many years for a variety of reactions, including steam reforming of methane, reforming of methanol, conversion of CO to CO2, water-gas shift, or oxidation of methanol to form formaldehyde, and oxidation of ethylene to form ethylene oxide. Packed bed catalyst designs are also used in some pollution control applications. Packed bed catalyst designs have always been negatively affected by pumping losses caused by pressure drop as the liquid or gas fluid flows through the packed bed.
Some of these packed bed reactions (for example, steam reforming of methane) mitigate the pressure drop problem by using large beads in the packed bed, ie, 10 mm or more. Less surface area, and sometimes less heat transfer is available with larger beads, but these reduced properties are acceptable in some cases. Other packed bed reactions cannot operate effectively without the properties of the smaller beads, with characteristic size of 6 mm or less.
It is also known to use beds packed with sorbent beads. Such packed beds will absorb or adsorb a particular species of gas or liquid from a mixture that is passed through the bed. Such beds also sometimes require small beads to operate effectively.
All such packed beds can be characterized as random or loose packed, with associated un-ordered or turbulent flow of gas or liquid through the bed. One problem with loose or random packed beds is that, when the metal container or enclosure surrounding the ceramic beads or media cools and contracts, the ceramic beads or media may be compacted, crushed, cracked or flaked, causing degradation of the beads or media, and the resulting powder/flakes tends to clog the bed.
Catalytic monoliths for reaction purposes are also known wherein a metallic foil is coated on both sides with an appropriate catalyst; one or more pieces of coated foil are then secured together to form the monolith; see, eg: U.S. Pat. Nos. 7,320,778 and 7,077,999. However, coating the foil with catalyst is an expensive and difficult task. There is a need for a simpler, less expensive, more effective way to achieve catalytic reactions and sorbent separations using catalytic or sorbent beads.